This invention relates to gas-cushion vehicles, that is to say, to vehicles for travelling over a surface and which, in operation, are supported above that surface, at least in part, by a cushion of pressurised gas, for example, air, formed and contained between the vehicle body and the surface.
When a gas-cushion vehicle travels over an undulating surface such as rough water or ground, it experiences changes in volume and thereby changes in pressure of the vehicle-supporting cushion, which changes result in the application of undesirable heave forces to the vehicle.